Automotive engines not only keep vibrating for the structure, but vibrate depending on the conditions of the ground while vehicles run. The vibrations are caused by not an independent factor, but various composite factors, vertically, laterally, and longitudinally.
The engines generate considerable vibrations due to a periodical change of the center position by the vertical motion of pistons and connecting rods, the inertia force in reciprocation in the axial direction of cylinders, and a periodical change of torque applied to a crankshaft from the connecting rods.
Accordingly, the engines are mounted on an engine mount to reduce vibration that is transmitted to the chassis frame or the car body.
A semi-active mount (active engine mount) that has been developed up to now is largely classified into a Bypass type using vacuum negative pressure and a volume-stiffness type using an electronic solenoid valve. The bypass type using vacuum negative pressure is difficult to manufacture, so the volume-stiffness type using a solenoid valve has been increasingly popularized.
The volume-stiffness type can be controlled by an electronic solenoid valve and does not generate a dynamic shoot-up when it is in an open mode (an idling mode), so it is very strong against vibration.
However, when it is in a close mode (driving mode), due to the relationship between a dynamic change rate and a loss factor, there are necessarily many errors in trade-off in which the loss factor is small when the dynamic change rate is large, and the loss factor can be slightly improved when the dynamic change rate is small, it has small dynamic change rate and loss factor in comparison to the by-pass type.
In connection with this matter, FIG. 1 provides a graph illustrating a loss factor of an active engine mount of the related art in driving and idling and it can be seen from the figure that the loss factor is 1.0 or less even in driving.
As a result, there is a need for an electronic active engine mount having the advantages of both of the by-pass type and the volume-stiffness type that can increase a loss factor at a high dynamic change rate, and if necessary, can reduce the dynamic change rate to increase an insulation ratio in driving.